MINNEAPOLIS -- Even though the Minnesota Vikings have whittled their cap space from nearly $40 million down to below $16 million, they're not closing the book after a busy first week of free agency moves.

General manager Rick Spielman said Friday that the Vikings will remain active, which includes some visits already scheduled for next week -- even though Spielman said he'll be chartering off to visit more college Pro Days starting Sunday.

"We'll continue to monitor the market. We'd like to still continue to fill some holes. We have some guys coming in next week on potential visits as of today and we'll see where that goes," Spielman said on a conference call. "But we're not, by any means, saying that we're completely finished."

Along with setting aside room for May's NFL draft, practice squad players and injury replacements, the Vikings appear to have little to work with -- but Spielman said he's watching out for value guys at needed positions, like added depth along the defensive line.

"Because you don't know what's going to happen or there are some guys that may be looking for a lot of money at this point but a week from now that could potentially change," Spielman said. "We'll continue to monitor that and if the market changes and we feel there is a good value there and a good player that can come in and help our ball club and wants to come in and compete, we'll definitely be looking at that."

Spielman, first-year coach Mike Zimmer and offensive coordinator Norv Turner were at Alabama's Pro Day on Wednesday, when Munnerlyn was in for his visit. The Vikings' brass were back in town by the next day to close the deal. It seems they'll be doing the same jet-setting as Spielman said they'll bounce around Pro Days all this month -- starting Sunday.

"You are down in Alabama one day because you have everything kind of lined up and next thing you know you are doing dinners and hosting free agents and then we're getting ready to head out on Sunday," Spielman said. "I'll be here doing tape all day [Friday] and all day [Saturday] and then we're heading out to some pro days next week."

The Vikings had Chicago Bears free agent defensive tackle Henry Melton in for a visit this week. Despite having a focus on youth, Spielman also said 33-year-old Kevin Williams is not out of the picture for added depth along the defensive line.

Former New York Jets' second-round pick Vladimir Ducasse is reportedly one of those players scheduled to visit the Vikings next week, but Spielman also said the offensive line will be a key target for the Vikings in May's NFL Draft.

Spielman said the Vikings are looking to bring back veteran lineman Charlie Johnson, who started at left guard last season.

"We bring 15 offensive lineman to camp and we're going keep our best eight or nine regardless of who we end up signing, who's going to be the starters and who's going to be the backups but we definitely want to add some youth, but would love to have Charlie Johnson back as well."